1. Field of the Invention
The invention relates generally to illuminated signs such as exit signs having either emergency or non-emergency capabilities and particularly to exit signs which can be configured to be illuminated by selected light sources and having a standard housing frame forming a basic housing unit of the differing configurations of the exit signs.
2. Description of the Prior Art
Possibly the most common form of illuminated sign is the exit sign which can take a variety of physical configurations and utilize one or more light sources of differing type. Exit signs having the capability of operation in emergency situations often use two different light sources, one light source for non-emergency operation on AC mains power and a second light source for operation on emergency power, usually DC power provided by a battery. In usual applications, exit signs are placed above doorways or in egress paths to indicate the most efficient manner of exiting an environmental space in the event of emergency conditions. Certain types of exit signage operate only in a non-emergency mode when mains power is available, such signage being referred to in the industry as "standard" signs. The term "emergency" exit signage generally refers to those exit signs which operate in both non-emergency and emergency modes with an emergency mode being defined as a condition wherein mains power becomes unavailable to operate the light source normally used in the non-emergency mode. Discontinuation of a normal power supply in "emergency" exit signage causes an alternate source of power, usually DC power from a battery contained within the exit sign, to operate either the light source also used in the non-emergency mode or a second light source which usually functions only under emergency conditions. While incandescent light sources have long been used for operation in both normal and emergency modes, other sources such as arrays of light emitting diodes have received substantial acceptance due to low energy operation and long life. The use of light emitting diodes in the normal, non-emergency mode provides great advantages when coupled with the use of incandescent lamps as the emergency light source. Prior exit signs have also employed light emitting diodes as the sole light source in both normal, non-emergency operation and in emergency operation, the light emitting diodes being typically powered by AC mains power in the non-emergency mode and by direct current such as a battery contained within the exit sign or by direct current supplied from externally of the exit sign. The variety of light sources now available results in the necessity of providing a number of particular exit sign constructions which are designed to facilitate use of a particular light source or a particular combination of light sources. A manufacturer of exit signs must therefore design, fabricate and maintain in inventory a variety of different exit sign housings most of which are limited to use with only a single light source or a particular combination of light sources. Exit signs not capable of emergency operation typically are comprised of housings which are not suitable for the fabrication of exit signage which embody emergency capability. Since cost is ever a factor in the manufacture of exit signage, it is further to be noted that the molding of exit sign housings from polymeric materials has become wide-spread. The cost of tooling for production of molded sign housings has further resulted in a need to produce a housing which can be utilized as the basic support and containment unit for exit signs of differing type and function.
A need therefore exits in the art to provide illuminated signs and particularly exit signs which are inexpensive to manufacture and operate regardless of operation as "standard" or "emergency" signage. The art further finds a need for sign housings capable of use either without modification or with only slight modifications such as in the molding process for fabrication of different types of signage including different versions of "standard" signage and "emergency" signage. Such modifications can be primarily accomplished in molding of a basic frame used as the primary structural unit in the assembly of multiple purpose sign housings. A basic housing frame configured according to the invention can be molded from polymeric materials and can contain and support light sources such as an array of light emitting diodes and the like including an emergency mode power supply such as a battery and circuitry necessary for operation of the sign. In a particular embodiment of the invention, a substrate such as a printed circuit board can be used as a platform to support an array of light emitting diodes and those circuit components including a battery necessary for operation of the light emitting diode array in both "standard" and "emergency" embodiments, the same array of light emitting diodes being preferably driven in both normal and emergency modes in the emergency embodiments. The printed circuit board platform is mounted by a support structure formed on a floor of the sign, the support structure acting to mount the platform with exceptional stability to prevent warping or other distortion of the platform which could degrade illumination of the indicia formed in one or more face panels of the sign. Disposition of the light emitting diode array near the floor of the sign allows the interior volume of the sign to be substantially vacant, thereby increasing illumination of the indicia such as by increased reflection of light from the interior "ceiling" of the sign as well as increased total internal reflection.
Accordingly, the various aspects of the invention act to reduce the costs of and improve the performance of exit signage and particularly exit signage intended as signage exhibiting low initial equipment costs as well as low operational costs.